Furnace grate with fire bars



y 6, 1955 M. v. u. PIETERSE 3,192,919

FURNACE GRATE WITH FIRE BARS Filed July 11, 1962 2 Sheets-Sheet 1 f 'er- Ah -7 July 6, 1965 M. V. U. PIETERSE FURNACE GRATE WITH FIRE BARS Filed July 11, 1962 2 Sheets-Sheet 2- United States Patent 3,192,919 FURNACE GRATE WITH FIRE BARS Marius van Uye Pieterse, Haanplein 24, The Hague, Netherlands Filed duly 11, 1962, Ser. No. 209,114 8 Claims. (Cl. 126-163) The invention relates to a furnace grate for use in effecting complete or substantially complete combustion of any kind of solid fuel, and especially for use in effecting combustion of fine granular coal, said grate being of a kind consisting of a side-by-side serie of fire bars provided along one or both of their longitudinal sideswith series of laterally projecting spaced ribs, flanges or tongues which form between them series of channels for the passage of air upwardly between adjacent bars, which channels may extend, as is known, one series in the opposite direction to the next adjacent series s othat the directions of incoming air alternate from bar to bar and such air penetrates to every part of the fuel resting on the fire bars without carrying with it on its way to the chimney small particles of unburnt fuel.

Each of said spaced ribs has, as has already been proposed, at its topand under-side two nose-shaped parts directed to the right respectively and to the left, which noses overlap each other.

Grates of the aforesaid kind have the disadvantage that they are not quite suitable for the combustion of fuel of varying degrees of coarseness or fineness, as unburnt small coals tend to fall through the air channels between the fire bars. 7

The object of the invention is to obviate or mitigate this disadvantage in a simple manner.

According to the present invention, each lower nose extending substantially from the ribs intersection with the perpendicular line drawn from the foremost point of the upper nose of the adjacent rib, terminates in a pointed end or edge directed more or less upwardly so that oblong channels are formed for supporting the sloped free face of the granular fuel and preventing the sliding away of tive air channel so that the velocity of the air is converted in pressure and a venturi-operation exists, the arrangement being such that the fine granular coal and 'cinders cannot become clogged because the air channel is freed or loosened at the venturi zone.

The object of the above stated concave inner side of the rib is to give the air for combustion an unhindered passage and to make easy the freeing or loosening and also to enable the ash and cinders to be removed unhindered.

Preferably also the cross-sectional areas of the air channels decrease in groups from the middle of the grate to the edges thereof so that more air for combustion is available in the middle than at the edges, this arrangement being especially suitable in a grate of which the bars extend in an inclined direction downwards from their outer ends to the middle.

Finally an important featureindependently of or com 3,192,919 Patented July 6, 1965 bined with the remaining features is that the furnace grate of the kind referred to, viz of trough shape, has the laterally projecting spaced ribs with which the fire bars are provided, which bars extend in an inclined direction from their outer ends to the middle, terimnating at their under sides in turned-up nose-shaped parts.

As regards this feature, it is remarked that by incorpora tion in a grate of which the lowermost noses lie in a horizontal plane as previously proposed, the fuel slope slides away when thefire bars of such a grate extend in an inclined direction, incontact with the grate according to the present invention with inclined fire bars, in which the slope does not slide away owing to the turned-up nose shaped parts at the underside of the ribs.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows a front view of a double grate with inclined or sloped fire bars.

FIG. 2 is a view similar to FIG. 1, showing the profiles of the ribs either of the next adjacent bar or at the opposite side of the same bar, as mirror images of FIG. 1.

FIG. 3 shows a top plan view of the grate, with the fire bars lying closely together throughout their lengths.

FIG. 4 shows a detail of FIG. 1, on an enlarged scale, and

FIG. 5 shows detail of FIG. 2, on an enlarged scale.

Referring to the drawings: i

The fire bars 1 are supported at their innerends upon a cross-shaped bearer 2 and at their outer ends upon the inner wall of a furnace 3.

Each fire bar is provided with spacedribs 4.

According to the drawing these spaced ribs 4, which are integral with .the bar, lie at one longitudinal side of each fire bar, or alternatively those ribs are on both longitudinal sides of the same bar.

Except for the ribs lying at the ends of the bars, all the ribs have'a similar profile.

Further, the ribs 4 form between them series of channels 5 for the passage of air'upwardly between adjacent bars, and the channels of successive series extend in directions one series opposite to the other, so that the direction of incoming air alternates from series to series and such air penetrates to every part of the fuel resting on the fire bars withoutcarrying with it on its way to the chimney small particles of unburnt fuel. J

The arrows in FIGS. 1, 2 and 3 indicate the direction of the combustion air through the air channels 5.

Each fire bar 1 has a series of ribs 4 each with two upper and lower nose-shaped parts 6 and 7 directed respectively to opposite ends of the rib, viz to the right and to the left, with the upper nose-shaped part of one rib overlapping the lower nose-shaped part of anext adjacent rib and, conversely the lower-nose-shaped part of the one rib overlapping the upper nose-shaped part of a next adjacent rib.

border to prevent passage of granular fuel through the air channels 5 past the lower nose-shaped parts 7 (hereinafter for convenience called noses) each lower nose 7 extends substantially from the intersection or the rib with the perpendicular line drawn from the foremost point of the upper nose 6 of the adjacent rib 4, and terminates in a pointed end or edge 8 directed more or less upwardly, sothat oblong channels are provided for supporting the sloped free face of said granular fuel while preventing the sliding away of the slope 9.

The pointed end or edge 8 of each lower nose 7 projects to such an extent in the direction of the concave inner side of the adjacent rib that said pointed end with respect to said inner side causes a constriction in the related air channel so that the velocity of the air is converted in pressure and a venturi-operation exists, the arrangement being such that the fine granular coal and cinders cannot become clogged because the air channel is freed at the venturi zone.

With regard to the concave form of the inner sides of the ribs, i.e. the sides lying opposite to the related pointed ends or edges 8, it is to be noted that this form serves not only to facilitate said freeing or loosening, but also to prevent ash and cinders from being caught in the air passage, and facilitate their removal.

The above-mentioned so-called turned-up noses '7 are especially desirable in a double grate of which the fire bars slope from the outer ends to the inner ends to form a trough, as the noses ensure that the sliding away of the slope 9,is prevented; although said turned-up noses 7 also can be provided in grates with horizontal bars.

It is thus clear that if a grate is provided which has the lower noses 7 lying in a horizontal plane, the slope 9 will slide away from its support when such a grate is lying in a sloped or inclined position.

The minimum cross-sectional areas in the air channels 5 of the trough-shaped grates as above described, decrease in groups from the middle of the grate to the outer edges thereof so that more air for combustion is available in the middle than at the edges, while the width of the air channels 5 at the top side of the fire bars 1 remains equal from channel to channel as illustrated in FIG. 3.

With reference to FIGS. 4 and 5, it will be noted that the angle x in both figures, formed by a perpendicular line drawn from the tip of the nose 6 of the rib 4 and the line defining the natural slope 9 of the fuel with respect to the horizontal plane (said angle may be called the sliding-angle), is smaller than the angle y which is formed by said perpendicular line and a line to the tip 8 of the nose 7; by this means substantially no unburnt fuel falls over the tip 8 into the ashpit.

It will be understood that the present invention is not restricted to the embodiment as described and illustrated, which may be varied without departing from the broad ideas of the invention.

Thus, it is possible to provide the ribs 4 of the fire bars 1, instead of at one longitudinal side of the bar, at

both longitudinal sides while the grate, instead of having its bars extending in an inclined direction downwards from their ends to the middle, may have its bars disposed in a horizontal plane.

What I claim is:

1. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of said fire bars being adapted to be supported at one end in the central area of the furnace and at the other end at a side of the furnace, each of said fire bars having a plurality of spaced ribs extending along the length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a fire bar having an upper end'forrning a substantially planar slope with the upper ends of the other ribs of the fire bar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each of the air channels between the ribs of each of said fire bars having a minimum cross-sectional area at one part thereof and the minimum crosssectional areas of the air channels between the ribs of each of said fire bars having maximum dimensions in the area of said one end of said fire bar and minimum dimensions in the area of said other end of said fire bar, the dimensions of said minimum cross-sectional areas decreasing from said one to said other end.

2. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of said fire bars being adapted to be supported at one end in the central area of the furnace and at the other end at a side of the furnace, each of said fire bars having a plurality of equidistantly spaced ribs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a fire bar having an upper end forming a substantially planar slope with the upper ends of the other ribs of the fire bar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each of the air channels between the ribs of each of said fire 'bars having a minimum cross-sectional area at one part thereof and the minimum cross-sectional areas of the air channels between the ribs of each of said fire bars having maximum dimensions in the area of said one end of said fire bar and minimum dimensions in the area of said other end of said fire bar, the dimensions of said minimum cross-sectional areas decreasing from said one to said other end.

3. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of said fire bars being adapted to be supported at one end in the central area of the furnace and at the other end at a side of the furnace, each of saidfire bars having a plurality of spaced ribs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each n'b of a fire bar having an upper end forming a substantially planar'slope with the upper ends of the other ribs of the fire bar, a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs 0f the fire bar passes through the lower end of the next adjacent rib of the fire bar, each rib having an undersurface and an oversurface each extending from the upper end to the lower end, the undersurface being of substantially concave configuration, each of the air channels between the ribs of each of said fire bars having a minimum crosssectional area at one part thereof and the minimum crosssectional are-as of the air channels between the ribs of each of said fire bars having maximum dimensions in the area of said one end of said fire bar and minimum dimensions in the area of said othe end of said fire bar, the

dimensions of said minimum cross-sectional areas decreasing from said one to said other end.

4. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of said fire bars being adapted to be supported at one end in the central area of the furnace and at the other end at a side of the furnace, each of said fire bars having a plurality of spaced ribs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a fire bar having an upper end forming a substantially planar slope with the upper ends of the other ribs of thefire bar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in amanner whereby a line through the upper end of a rib perpendicular to the plane of .the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each rib having an undersurface and an ove'rsurface each extending from the upper end to the lower end, the undersurface being of substantially concave configuration and the oversurface being of substantially planar configuration, each of the air channels between the ribs of each of said fire bars having a minimum cross-sectional area at one part thereof and the minimum cross-sectional areas of the air channels between the ribs of each of said fire bars having maximum dimensions in the area of said one end of said fire bar and minimum dimensions in the area of said other end of said fire bar, the dimensions of said minimum crosssectional areas decreasing from said one to said other end.

5. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of said fire bars being adapted to be supported at one end in the central area of the furnace and at the other end at a side of the furnace, each of said fire bars having a pluarlity of spaced ri'bs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a fire bar having an upper end forming a substantially planar slope with the upper ends of the other ribs of the fire bar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each rib having an undersurface and an oversurface each extending from the upper end to the lower end, the undersurface being of substantially concave configuration and the oversurfiace being of substantially planar configuration, and a nose section extending from the lower end of the rib transversely to the oversurface of the rib, each of the air channels between the ribs of each of said fire bars having a minimum cross-sectional area at one part thereof .and the minimum cross-sectional areas of the air channels between the ribs of each of said fire bars having maximum dimensions in the area of said one end of said fire bar and minimum dimensions in the area of 'said other end of said fire bar, the dimensions of said minimum cross-sectional areas decreasing from said one to said other end.

6. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of said fire bars being adapted to be supported at one end in the central area of the furnace and at the other end at a side of the furnace, each of said fire bars having a plurality of spaced ribs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a fire bar having an upper end forming a substantially planar slope with the upper ends of the other ribs of the fire bar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each rib having an undersurface and an oversurface each extending from the upper end to the lower end, the undersurface being of substantially concave configuration and the oversurface being of substantially planar configuration, and a nose section extending from the lower end of the rib transversely to the oversurface of the rib, each of the air channels between the ribs of each of said fire bars having a minimum cross-sectional area at one part thereof formed by the end of the nose section of each of said ribs farthest from the oversurface thereof and the undersurface of the next adjacent rib, and the minimum crosssectional areas of the air channels betwen the ribs of each of said fire bars having maximum dimensions in the area of said .oneend of said fire bar and minimum dimensions in the area of said other end of said fire bar, the

dimensions of said minimum cross-sectional areas de-' creasing from said one to said other end.

7. A furnace grade for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising two groups of fire bars each having a plurality of fire bars adapted to be supported in side by side relation in a furnace, each of the fire bars of one group being adapted to be supported at one end in the central area of the furnace and at the other end at one side of said furnace and each of the fire bars of the other group being adapted to be supported at one end in the central area of the furnace and at the other end at the opposite side of the furnace, each of the fire bars of each of the two groups of fire bars hav ing a plurality of spaced ribs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a fire bar having an upper end forming a substantially planar slope with the upper ends of the other ribs of the firebar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each of the air channels between the ribs of each of said fire bars having a minimum cross-sectional area at one part thereof and the minimum cross-sectional areas of the air channels betwen the ribs of each of said fire bars having maximum dimensions in the area of said one end of said fire bar and minimum dimensions in the area of said other end of said fire bar, the dimensions of said minimum cross-sectional areas decreasing from said one to said other end.

8. A furnace grate for effecting combustion of fine granular fuel in a furnace having a central area and spaced opposite sides, comprising, two groups of fire bars each group being adapted to incline downward from a side,

of the furnace to the center thereof and each group of fire bars having a plurality of fire bars adapted to be supported in side by said relation in the furnace, each of the fire bars of one group being adapted to be supported at one end in the central area of the furnace and at the other end at one side of the furnace and each of the fire bars of the other group being adapted to be supported at one end in the central area of the furnace and at the other end at the opposite side of the-furnace, each of the fire bars of each of the two groups of fire bars having a plurality of spaced ribs extending along its length and projecting laterally therefrom to form a plurality of air channels between said spaced ribs, each rib of a tire bar having an upper end forming a substantially planar slope with the upper ends of the other ribs of the fire bar and a lower end spaced from its upper end and underlapping the upper end of the next adjacent rib of the fire bar in a manner whereby a line through the upper end of a rib perpendicular to the plane of the slope formed by the upper ends of the ribs of the fire bar passes through the lower end of the next adjacent rib of the fire bar, each of the air channels between the ribs of each of said fire bars having a minimum cross-sectional area at one part thereof and the minimum cross-sectional areas of the air channels between the ribs of each of said firebars having maximum dimensions in the area of said one end of said fire bar 7 E5 and minimum dimensions in the area ofeeid other end of 2,116,024 5/38 Hehnick 2 126163 said fire bar, the dlrnensrons of said mmlrnum cross-sec- FOREIGN PATENTS tional areas decreasing from said one to said other end.

1,225,342 2/60 France.

References Cited by the Examiner I 5 0 6/ 5 Germany.

552,467 6/32 Germany. UNITED STATES PATENTS 242,872 11/25 Great Britain.

1,625,556 4/27 Lomshakoff 126-463 X 1,762,655 6/30 Erdos 126163 X JAMES \V. WESTHAVER, Primary Examiner.

802,960 4/31 126163 5 10 PERCY L. PATRICK, Examiner.

1,817,484 8/31 Goebel 12616: 

1. A FURNACE GRATE FOR EFFECTING COMBUSTION OF FINE GRANULAR FUEL IN A FURNACE HAVING A CENTRAL AREA AND SPACED OPPOSITE SIDES, COMPRISING A PLURALITY OF FIRE BARS ADAPTED TO BE SUPPORTED IN SIDE BY SIDE RELATION IN A FURNACE, EACH OF SAID FIRE BARS BEING ADAPTED TO BE SUPPORTED AT ONE END IN THE CENTRAL AREA OF THE FURNACE AND AT THE OTHER END AT A SIDE OF THE FURRNACE, EACH OF SAID FIRE BARS HAVING A PLURALITY OF SPACED RIBS EXTENDING ALONG THE LENGTH AND PROJECTING LATERALLY THEREFROM TO FORM A PLURALITY OF AIR CHANNELS BETWEEN SAID SPACED RIBS, EACH RIB OF A FIRE BAR HAVING AN UPPER END FORMING A SUBSTANTIALLY PLANAR SLOPE WITTH THE UPPER ENDS OF THE OTHER RIBS OF THE FIRE BAR AND A LOWERED END SPACED FROM ITS UPPER END AND UNDERLAPPING THE UPPER END OF THE NEXT ADJACENT RIB OF THE FIRE BAR IN A MANNER WHEREBY A LINE THROUGH THE UPPER END OF A RIB PERPENDICULAR TO THE PLANE OF THE SLOPE FORMED BY THE UPPER ENDS OF THE NEXT ADJACENT RIB OF PASSES THROUGH THE LOWER END OF THE NEXT ADJACENT RIB OF THE FIRE BARE, EACH OF THE AIR CHANNELS BETWEEN THE RIBS OF EACH OF SAID FIRE BARS HAVING A MINIMUM CROSS-SECTIONAL AREA AT ONE PART THEREOF AND THE MINIMUM CROSSSECTIONAL AREAS OF THE AIR CHANNELS BETWEEN THE RIBS OF EACH OF SAID FIRE BARS HAVING MAXIMUM DIMENSIONS IN THE AREA OF SAID ONE END OF SAID FIRE BAR AND MINIMUM DIMENSIONS IN THE AREA OF SAID OTHER END OF SAID FIRE BAR, THE DIMENSIONS OF SAID MINIMUM CROSS-SECTIONAL AREAS DECREASING FROM SAID ONE TO SAID OTHER END. 